It is becoming apparent that, in the future, battery systems will increasingly be used for stationary applications, for example solar and wind power plants, for mobile applications, for example vehicles, such as hybrid and electric vehicles, and in the consumer sector, for example laptops and cell phones, these systems having to meet very high requirements with respect to safety, reliability, power and lifetime.
An important parameter for the power is the energy density, which is given for example in watt-hours per kilogram (Wh/kg). The capacity of a galvanic cell is determined by what is known as the active or electrochemically active materials. Apart from these materials, galvanic cells also have what are known as passive materials, such as separators, insulators, electrode binders and housing or package elements, the weight of which, like the weight of the active materials, has an influence on the energy density.
Predestined for a wide area of use are, in particular, lithium-ion cells, since they are distinguished inter alia by high energy densities of the active materials and an extremely low self-discharge. Lithium-ion cells have a positive electrode (cathode) and negative electrode (anode). The active material of the negative electrode (anode) of a lithium-ion cell is designed here for the reversible insertion (intercalation) of lithium ions (Li+) or extraction (deintercalation) again of lithium ions (Li+), and is therefore also referred to as intercalation material. Conventionally, graphite is used on the anode side as intercalation material.
Another attractive battery system is that of rechargeable metallic lithium systems, which likewise have a positive electrode (cathode) and negative electrode (anode), in which however the active material of the negative electrode (anode) is not lithium-intercalating material, but metallic lithium or a lithium alloy.
In order to achieve great mechanical stability and meet high safety requirements, for example in the case of vehicles, lithium-ion cells and lithium cells with a metallic lithium anode for such applications are conventionally protected from environmental influences, in particular from any entry of moisture into the interior of the cell, by purely metallic hard shell cell housings, known as hard case housings. At present, such hard shell cell housings are usually produced from aluminum by cold deep-drawing methods. Apart from mechanical protection, metallic hard shell cell housings also protect the components of the cell(s) housed therein from moisture, since the metallic housing material also serves as a moisture or vapor barrier.